In wavelength multiplexing optical information communication, a variable band spectrum shaper (VBS) is known as a device that controls the phase and strength of optical wavelength multiplexing signals. For example, a VBS is disclosed in JP 2008-310190 A (Patent Literature 1 described below).
In addition, a multi-input multi-output optical polarization controller is known as a device for performing polarization control for each wavelength component and also for outputting optical signals of a plurality of wavelengths the polarization plane of each of which is controlled. A multi-input multi-output optical polarization controller is disclosed in, for example, JP 8-262394 A (Patent Literature 2 described below). This multi-input multi-output optical polarization controller is capable of controlling the polarization state of each of wavelength components included in the optical wavelength multiplexing signals by separating optical wavelength multiplexing signals depending on the wavelengths and by multiplexing the optical wavelength multiplexing signals after controlling the polarization plane of each of the wavelength components.